Sometimes, a lot of times I end up spinning only 270 degrees.
Or my leg is straight from about 170 until say 270, then I hook or bend my my lower leg, which gives me the rest of the spin. Spin hook kick is just the term I feel comfortable with. Others call it back spinning kick, back spinning hook kick, spinning whip kick, and I even hear wheel kick every once in a while. I've come to the conclusion that there is absolutely no standardization for this kick. Everyone has their own theory and everyone does it slightly different, with different drills, more so than any other kick.